Oh the things I have seen! – (at sea)

Three new things I have learnt about the world over the last two weeks.

1) The ocean is humungous. This first point seems obvious. Everyone knows the Earth’s surface is two-thirds covered by water, but I’d never fully appreciated how biased my perspective was as a former land dweller. There is an absurd amount of water! The continents are merely swimming in a vast bathtub. If aliens landed right now they’d probably make friends with the dolphins before us.

2) It is teeming with flying fish. I’d never heard of a flying fish before getting on this ship (literally a fish with wings) but I am now convinced they must be the most populous animal on this planet based on the sheer number I’ve seen. They jump out of the water (presumably to avoid predators), and glide through the air before plopping back into the sea. The first time someone said they saw one we all thought they had lost their mind, but it’s undeniable now. It’s rare to have a day go by without seeing one, or hundreds.

3) There is a whole world down there and we’ve never seen it before. One of the goals of this project was to study oceanic plates that were free from significant volcanic activity. A nice “apparently” smooth flat patch of seafloor was chosen around 6° South, 133° West (check it out on Google Earth!). This bathymetry is primarily based on satellite data of the sea surface and is relatively coarse. Now we are in the study area we are mapping the landscape of the ocean bottom at high resolution using multi-beam. This sends out a high pitched sound and listens to the pattern of echoes (i.e. reflections) that return. Only 5% of the ocean floor has ever been mapped in such a way. Every feature we find is a part of our planet that we are seeing for the very first time, and it is incredible!

There is so much topography down there it blows my mind. We’ve traversed mountains, valleys, cliffs, and seamounts galore! So much for being nice smooth seafloor. Yesterday we passed over a sheer drop of 400m, like a linear trough bounded on each side by vertical cliffs. It quickly became known as the “Pit of Sorrows”.  At the time of writing 12 new seamounts (circular volcanic mounds) have been discovered. Some of these have clear craters at the top, or missing chunks where there has been a slump. The biggest seamounts we’ve seen are almost 1000m high, including the now infamous “Mount Scurvy Turtle”.

One of the biggest surprises to me so far has been the consistency of the abyssal hill fabric. This appears as a series of linear ridges and valleys, several hundred metres high, which seemingly go on repeating forever. Their edges are sometimes separated by sharp boundaries that seem indicative of faulting. It is thought that this abyssal hill structure is inherited at the mid-ocean ridge where the oceanic crust is created. In our case, the seafloor below formed along the East-Pacific Rise and the abyssal hill fabric has a super consistent north-south orientation. At least if we ever get lost out here we’ll know which way is north!

By Caroline Eakin

mt_scurvy_lowres
Mount Scurvy Turtle, as imaged by our MultiBeam software. We’ve never seen a scurvier turtle seamount than this. 
IMG_9810
Deploying an OBS off the back of the ship. Caroline (center, holding the coil of rope) is about to pull the release as soon as it touches the water.
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